Optical brighteners their composition their production and their use

ABSTRACT

Optical brighteners (P AB ) of formula 
                         
wherein
         each n independently signifies 1 or 2,   the group SO 3 M shown with the floating bond is linked to the position 4 or 5,   each M independently signifies an equivalent of a non-chromophoric cation, each M′ independently signifies hydrogen or M,   at least a part of the cations M of (P AB ) are cationic groups of a polycationic polyol/epichlorohydrin/amine polymer (P A ), which contains quaternary ammonium groups in salt form as heteroatomic ring members or chain members, any others being cations selected from alkali metal cations, unsubstituted ammonium and ammonium substituted with C 1-3 -alkyl or/and C 2-3 -hydroxyalkyl,   the polycationic polymer (P A ) is a polymer which is at least in part crosslinked over one or more of its quaternary ammonium groups,   any other counterions to the cationic groups of (P A ) being non-chromophoric anions of low molecular acids,
 
and the ratio of the total anionic groups in the anionic optical brightener portion of (P AB ) to the total of cationic ammonium groups in the polycationic polymer (P A ) portion of (P AB ) is ≧80/100,
 
and their aqueous compositions (W), their production and their use, also in combination with white pigments or fillers, in particular for the production of optically brightened paper.

In the production of paper it is usual to employ retention agents,dewatering agents and/or fixatives in order to improve the speed ofproduction or other properties and yield of the product. These adjuvantsare mostly of cationic character, and if it is desired to produce anoptically brightened paper, care should be taken that with the use of ananionic optical brightener there does not occur a precipitation byinteraction of the anionic and cationic substances. In order to avoidsuch an undesirable precipitation, the cationic agents are usually addedat a sufficient time after the addition of the anionic component, eitherwithin a very short time range immediately before sheet formation (i.e.a few seconds before conveying the pulp to the paper sheet forming partof the assembly) or after sheet formation.

In Japanese Kokai JP 62-106965 A2 there are described opticalbrighteners of the 4,4′-bis-triazinylamino-stilbene -2,2′-disulphonicacid series produced by reaction of 2 molar proportions of cyanuricchloride with 2 molar proportions of aniline-2,5-disulphonic acid, thenwith one molar proportion of 4,4′-diaminostilbene-2,2′-disulphonic acidand finally with 2 molar proportions of certain defined aminoacids(including among others also aspartic acid and glutamic acid) which maybe the natural L-form or the synthetic D,L-form; they are described insalt form, in particular in sodium salt form, as optical brighteners ofhigh water solubility. With regard to their use for the opticalbrightening of paper, it is stated that they are not efficient for useas internal additives, i.e. for adding in the pulp slurry before makingthe paper.

In WO-A-99/67317 there are described aqueous solutions of polycationicpolymers containing quaternary ammonium groups in salt form asheteroatomic chain members or ring members of the polymer, wherein apart of the counter-ions to the quaternary cationic groups are anionicgroups of anionic optical brighteners, containing at least one anionicgroup, in which the cationic quaternary ammonium groups are insubstantial excess over the anionic groups of the anionic opticalbrighteners, in particular in the range of 100/60 to 100/2. The aqueoussolutions of these combined products are of high stability and providemulti-functional agents that combine the activity of the opticalbrighteners and of the cationic polymers (e.g. as retention assistant,drainage assistant or fixative in paper production), which in theproduction of optically brightened paper allows the addition of opticalbrightener together with the cationic polymer, e.g. by adding it to thestock at any time before sheet formation. (Product combinations of thiskind are also described in WO-A-01/46323 for white mineral pigments.)The limited ratio of polymer to optical brightener does, however, limitaccordingly the possibility of using high proportions of opticalbrightener or low proportions of cationic polymer so that theseproducts, although highly effective in a certain range, may not sufficeto fulfil the requirements of the full range of base paper or boardqualities as may occur in paper industry. If the proportion of theexemplified optical brighteners to the exemplified polymers is increasedto a ratio of anionic groups of the total anionic optical brighteners tocationic quaternary ammonium groups of the total cationic polymer to aratio substantially above 60/100, especially above 80/100, so as to givea prevailing anionic character—as resulting from the total equilibriumof the strongly anionic sulpho groups and optionally any weakly anioniccarboxy groups on the one side and the cationic quaternary ammoniumgroups on the other side—to the combined product, the viscosity andstickiness of the obtained composition diluted with water, as would berequired for use e.g. in papermaking, increases accordingly withincreasing anionicity to give a viscous and sticky mass (“chewinggum-like”) up to a hard mass, which is unusable for practical purposes,in particular in papermaking.

It has now surprisingly been found that with the below—overallanionic—combination (P_(AB)) of the defined particular opticalbrighteners and the defined particular polymers it is possible toproduce fluid and readily dilutable concentrated aqueous compositions ofhigh stability, in which the ratio of anionic groups in the opticalbrighteners to the cationic quaternary ammonium groups in the polymer is80/100 or more, so that any desired high proportion of opticalbrightener to polymer becomes available as may suit any requirement forthe production of the most various optically brightened paper and boardqualities.

The invention relates to the defined combined products (P_(AB)), theiraqueous compositions, their production and their use.

The invention thus provides an optical brightener (P_(AB)) of formula

wherein

-   -   each n independently signifies 1 or 2,    -   the group SO₃M shown with the floating bond is linked to the        position 4 or 5,    -   each M independently signifies an equivalent of a        non-chromophoric cation,    -   each M′ independently signifies hydrogen or M,    -   at least a part of the cations M of (P_(AB)) are cationic groups        of a polycationic polyol/epichlorohydrin/amine polymer (P_(A)),        which contains quaternary ammonium groups in salt form as        heteroatomic ring members or chain members, any others being        cations selected from alkali metal cations, unsubstituted        ammonium and ammonium substituted with C₁₋₃-alkyl or/and with        C₂₋₃-hydroxyalkyl,    -   the polycationic polymer (P_(A)) is a polymer which is at least        in part crosslinked over one or more of its quaternary ammonium        groups,    -   any other counterions to the cationic groups of (P_(A)) being        non-chromophoric anions of low molecular acids,        and the ratio of the total anionic groups in the anionic optical        brightener portion of (P_(AB)) to the total of cationic ammonium        groups in the polycationic polymer (P_(A)) portion of (P_(AB))        is ≧80/100.

The invention further provides a liquid aqueous optical brightenercomposition (W) comprising an optical brightener (P_(AB)).

The process for the production of the optical brighteners (P_(AB)) asdefined above and their compositions (W) is in particular characterisedin that

-   (B) an anionic optical brightener of the formula

-   -   wherein        -   each n independently signifies 1 or 2,    -   and the group SO₃H shown with the floating bond is linked to the        position 4 or 5, in free acid or alkali metal or/and ammonium        salt form, wherein ammonium is unsubstituted or substituted with        C₁₋₃-alkyl or/and with C₂₋₃-hydroxyalkyl,    -   optionally in the form of an aqueous dispersion or solution,        is added to an aqueous solution of

-   (P_(A)) a polycationic polyol/epichlorohydrin/amine polymer    containing quaternary ammonium groups in salt form as heteroatomic    chain members or ring members of the polymer, which is at least in    part crosslinked over one or more of these quaternary ammonium    groups and in which the counter-ions to the cationic quaternary    ammonium groups are anions of mineral acids, anions of low molecular    carboxylic acids or anions deriving from a quaternizing agent,    or an aqueous solution of (B) in the form of the free acid or alkali    metal salt, is added to an aqueous solution of a precursor (P_(PA))    Of (P_(A)), and if it has been added to a precursor (P_(PA)) Of    (P_(A)), it is further reacted to form (P_(A)) or respectively    (P_(AB)),    in such an equivalents ratio that the total anionic groups in the    anionic optical brightener (B) to the total of cationic ammonium    groups in the polycationic polymer (P_(A)) is ≧80/100, and the    obtained product (P_(AB)) is in the form of a liquid aqueous    composition (W).

In formula (I) and in formula (II) the group SO₃M or SO₃H shown with thefloating bond is preferably linked to the position 5.

Where M is not a counterion—in particular a quaternary ammoniumcation—of (P_(A)) it is an alkali metal cation (preferably lithium,sodium or potassium, more preferably sodium) or ammonium which is eitherunsubstituted or substituted with C₁₋₃-alkyl or/and C₂₋₃-hydroxyalkyl(preferably mono-, di- or tri-ethanol- or -isopropanol-ammonium); amongthese cations the alkali metal cations are preferred, especially sodium.

The radicals of the formula

are radicals of aspartic or glutamic acid, optionally in M-salt form,and may be the radical of D-, L- or DL-aspartic or -glutamic acid,optionally in M-salt form.

The optical brighteners (B) may be employed in any form as commerciallyavailable, e.g. as powders or granules, which may be dissolved in waterbefore combination with (P_(A)) or, with particular advantage, they maybe employed in the form of an aqueous solution directly from production.Usually they are produced in a three-stage reaction sequence by reactingcyanuric chloride first with aminobenzene-2,4- or -2,5-disulphonic acid,then with 4,4′-diaminostilbene-2,2′-disulphonic acid and finally withaspartic or glutamic acid, optionally in salt form, in aqueous mediumunder dehydrochlorinating conditions (e.g. the first chlorine at pH 4–7and at 5–15° C., the second chlorine at pH 6–9 and at 10–40° C., and thethird chlorine at pH 8–11 and at 60–100° C., with addition of alkalimetal hydroxide).

The quaternary ammonium groups in (P_(A)) are covalently linked to atleast two carbon atoms of the polymer. The polymers (P_(A)) areadvantageously of aliphatic character. They may contain furtherheteroatoms, in particular oxygen atoms and/or non-quaternary aminogroups. The heteroatoms in the polymer are preferably at a distance of 2to 6 carbon atoms from each other.

The polymers (P_(A)) are epichlorohydrin derived polyquaternarypolymers, in particular reaction products of epichlorohydrin withpolyols and amines, preferably secondary and/or tertiary amines, underconditions leading to at least partial crosslinking.

More particularly, the epichlorohydrin-derived polymers (P_(A)) arepolyquaternary, at least partially crosslinked polymers obtainable by atwo- or three-stage synthesis, in which in the first stageepichlorohydrin is reacted with a polyol to give a chloroterminatedadduct (P_(PA)), and in the second stage the chloroterminated adduct(P_(PA)) is reacted with an at least bifunctional secondary or tertiaryamine in order to obtain a crosslinked product with quaternary ammoniumgroups in the polymer structure; if any terminal chlorine is stillpresent in the reaction product, this may be reacted in a third stagee.g. with a monofunctional tertiary amine.

As starting polyols there may be employed preferably aliphatic hydroxycompounds, in particular poly-functional alcohols, preferablyoligohydroxy compounds with preferably two to six carbon atoms andpolyalkylene glycols of average molecular weight {overscore (M)}_(W)preferably ≦2000 and wherein alkylene contains 2–4 carbon atoms.

Suitable hydroxy compounds are in particular oligofunctional aliphaticalcohols and/or poly-(C₂₋₄-alkylene)glycols, especially bi- tohexa-functional aliphatic alcohols with up to six, preferably three tosix, carbon atoms in the hydrocarbon radical, in particular of thefollowing formulaX—(OH)_(x1)  (IIIa),in which

-   -   X signifies the x1-valent radical of a C₃₋₆-alkane        and x1 signifies a number from 3 to the number of carbon atoms        in X,        or a mixture of oligohydroxyalkanes of formula (IIIa),        or a mixture one or more oligohydroxyalkanes of formula (IIIa),        with a C₂₋₃-alkanediol,        or polyalkyleneglycols, in particular of the average formula        HO-(Alkylene-O)_(x2)—H  (IIIb),        wherein    -   Alkylene signifies C₂₋₄-alkylene        and x2 signifies a number from 2 to 40.

Preferred compounds of formula (IIIa) are those of formulaH—(CHOH)_(x1)—H  (IIIa′)with x1′ being 3 to 6.

Alkylene in formula (IIIb) is ethylene, propylene and/or butylene andthe polyalkyleneglycols of formula (IIIb) may be homo- or copolymers,preferably water soluble products (with a solubility in water of atleast 10 g/l at 20° C. and pH 7). As polyalkyleneglycols of formula(IIIb) there are preferably employed polyethyleneglycols orcopolyalkyleneglycols containing a prevailing molar proportion ofethyleneoxy-units. More preferably there are employedpolyethyleneglycols, i.e. compounds of formula (IIIb) in which Alkylenesignifies only ethylene.

By the reaction of the hydroxy groups with the epichlorohydrin the epoxyring of the epichlorohydrin is opened and a corresponding adduct isformed which contains a 2-hydroxy-3-chloro-propyl-1 radical. Thisreaction is preferably carried out in the absence of any other solventand, especially for hydroxy, in the presence of a catalyst, which ise.g. a Lewis acid, preferably boron trifluoride e.g. in the form of itsetherate or acetic acid complex. This reaction is exothermic and theepichlorohydrin reacts with the available hydroxy groups and, asreaction proceeds, may also react with a hydroxy group of a2-hydroxy-3-chloropropyl-1 radical formed during the reaction, so thatsome of the hydroxy groups in a polyfunctional starting reactant [e.g.of formula (IIIa)] may even remain non-reacted. Depending on the molarratio, on the functionality of the starting hydroxy-compound and on itsconfiguration—especially if x1 in formula (IIIa) is 4 to 6—the degree ofreaction of the x1 OH groups with epichlorohydrin may vary, and may e.g.be in the range of 50 to 95%, mostly 70 to 90%, of the total number ofOH groups originally present in the starting polyol. The obtained adduct(P_(PA)) is a chloro-terminated product.

The chloroterminated adduct (P_(PA)) is then reacted with a suitableamine to produce a polyquaternary crosslinked product, preferably with acrosslinking reactant that is capable of providing a bridging quaternaryammonium group, which suitably is a preferably aliphatic tertiaryoligoamine or secondary monoamine. Such amines may for instance bereaction products of epichlorohydrin with a primary or secondary amine,for instance with mono- or di-(C₁₋₄-alkyl)-amines, mono- ordi-(C₂₋₄-hydroxyalkyl)-amines or oligoamines with 2 to 4 carbon atoms inthe alkylene bridge, such as mono- or dimethylamine, mono- ordiethylamine, mono- or diisopropylamine, mono- or diethanolaamine, mono-or diisopropanolamine, ethylenediamine, propylenediamine,butylenediamine, diethylenetriamine, triethylenetetramine,tetraethylenepentamine or N-(2-aminoethyl)-ethanolamine, or preferablythey correspond to the following formula

in which

-   -   Y signifies C₂₋₃-alkylene,    -   y signifies a number from 0 to 3,    -   R′ signifies C₁₋₃-alkyl or C₂₋₃-hydroxyalkyl        and R″ has a significance of R′, if y is 1 to 3, or signifies        hydrogen, if y is 0,        especially as a reactant leading to a crosslinking, where the        starting oligohydroxy compound is of formula (IIIa).        or to the following formula

wherein

-   -   R′″ signifies hydrogen or C₁₋₃-alkyl        and w signifies a number from 2 to 6,        the amines of formula (V) being especially suitable as        reactants, where the starting oligo-hydroxy compound is of        formula (IIIb).

For an optional chain-terminating, quaternizing reaction there may e.g.be employed a tertiary monoamine preferably of formula.N(R′)₃  (VI).

As amino compounds of formulae (IV), (V) and (VI) there may be employedknown amines. The C₁₋₃-alkyl radicals in R′, R″ and R′″ may be methyl,ethyl, propyl or isopropyl, the lower molecular ones being preferred,especially methyl. The C₂₋₃-hydroxyalkyl radicals are preferably2-hydroxyethyl or -propyl. Among the C₁₋₃-alkyl radicals and theC₂₋₃-hydroxyalkyl radicals the C₁₋₃-alkyl radicals are preferred,especially methyl. The index y may be any number from 0 to 3 preferably0 to 2, more preferably 0 or 1. Representative amines of formula (IV)are dimethylamine, diethanolamine, tetramethylethylenediamine,tetramethylpropylenediamine,N,N-diethanol-N′,N′-dimethylethylenediamine,pentamethyldiethylenetriamine and hexamethyltriethylenetetramine, amongwhich the difunctional amines, in particular the lower molecular ones,are preferred, especially dimethylamine and tetramethylethylenediamine.In formula (V) the index w preferably is 2 or 3. Representative aminesof formula (V) are N,N-dimethylaminopropylamine,N,N-diethanolaminopropylamine, tetramethylethylenediamine,tetramethylpropylenediamine andN,N-diethanol-N′,N′-dimethylethylenediamine. Representative amines offormula (VI) are trimethylamine, triethylamine and triethanolamine,among which trimethylamine and triethylamine are preferred.

The polycationic polyquaternary products (P_(A)) or the opticalbrighteners (P_(AB)) are polymers at least insofar as either thereaction of (P_(PA)) with the amine leads to a polymer or the startingproduct is polymeric (e.g. is a polyalkylene glycol) or both.

The molar ratio of quaternizing amine to epichlorohydrin adduct (P_(PA))is suitably chosen so that a product of polymeric character is produced.The molar ratio of quaternizing amine to epichlorohydrin adduct to acompound of formula (IIIa) is preferably chosen so that for everymole-equivalent of adduct referred to chlorine there is employed 0.5mole of crosslinking amine, preferably of formula (IV), ±30%, e.g. ±10%.The molar ratio of quaternizing amine to epichlorohydrin adduct of acompound of formula (IIIb) is preferably chosen so that for everymole-equivalent of adduct referred to chlorine there is employed 1 moleof amine of formula (IV) ±40%, e.g. ±20%. The molar ratio ofquaternizing amine to epichlorohydrin adduct of a compound of formula(IIIb) is preferably chosen so that for every mole-equivalent of adductreferred to chlorine there is employed 0.9 mole of amine of formula(V)±40%, e.g. ±20% (if both R′″ are hydrogen) or 0.5 mole of amine offormula (V)±30%, e.g. ±10% (if both R′″ are other than hydrogen) or 0.7mole of amine of formula (V) ±35% e.g. ±15% (if one R′″ is hydrogen andthe other is other than hydrogen).

The reaction of quaternizing amine with the adduct is carried outpreferably in aqueous medium and preferably with heating, e.g. at atemperature in the range of 50 to 100° C., preferably 60 to 90° C.During the reaction, at least at the beginning, the basicity of theamine is sufficient for the quaternizing alkylation of the amine withthe adduct, i.e. with the chloride used as an alkylating agent. The pHof the reaction mixture is preferably in the range of 4 to 9, at thebeginning being preferably in the range of 7 to 9. As reaction proceeds,the alkalinity of the mixture and the concentration of crosslinkingamine diminish. If in the reaction product there is present a proportionof covalently linked chlorine which is higher than desired, there maye.g. be added a further reactant which is a monofunctional tertiaryamine and/or, if the starting crosslinking reactant is a secondarymonoamine, there may be added a suitable strong base, such as an alkalimetal hydroxide, preferably sodium hydroxide, so that the pH ispreferably maintained in the range of 7 to 9. When the reaction hascompleted or has reached the desired degree, the reaction mixture issuitably acidified by addition of a conventional acid, preferably amineral acid (such as hydrochloric acid, sulphuric acid or phosphoricacid) or a low molecular aliphatic carboxylic acid e.g. with 1 to 6carbon atoms (such as formic acid, acetic acid, citric acid or lacticacid), preferably to reach a pH below 7, more preferably in the range of4 to 7, most preferably in the range of 5 to 6.5. The progress of thereaction may be followed by checking the viscosity of the reactionmixture, which gives an empirical impression of the degree ofcrosslinking, i.e. quaternization. A suitable viscosity is e.g. in therange of 200 to 3000 cP.

In the production of (P_(A))—in the absence of (B)—the concentration ofthe reactants is preferably chosen in such a way that the concentrationof (P_(A)) in the resulting aqueous product is in the range of 10 to75%, preferably 20 to 70% by weight.

Preferred polymers (P_(A)) are:

-   -   (P_(A1)) polymers obtained by reaction of epichlorohydrin with        oligohydroxyalkanes, in particular of formula (IIIa) or        preferably (IIIa′), and further quaternizing reaction with        amines,        and (P_(A2)) polymers obtained by reaction of epichlorohydrin        with a polyalkyleneglycol, in particular of formula (IIIb),        preferably a polyethyleneglycol, and further reaction with        quaternizing amines.

Among the above are preferred (P_(A1)).

For the production of (P_(AB)), the produced polymer (P_(A)), if desiredin admixture with another cationic polymer, especially with a cationicstarch, e.g. in the weight ratio of the latter to (P_(A)) of up to 20%,expediently in the form of an aqueous solution, may be combined with anaqueous solution of (B). Preferably however—for the production of(P_(AB))—(P_(A)) is not combined with any other cationic polymers.According to one feature of this process, the aqueous solution of (B) isadded to the aqueous solution of (P_(A)), preferably stepwise and withheating, e.g. at temperatures in the range of 40° C. to the boil,preferably 40 to 90° C. According to a preferred feature of the processfor the production of (P_(AB)), the solution of (B) is added to (P_(PA))before polymerisation and/or crosslinking of (P_(A)) has completed. Forthe production of a composition (P_(AB)) from (P_(A1)) or (P_(A2)) it ispreferred to add at least a part of the optical brightener (B) beforethe crosslinking reaction has completed and to add any remaining portionof the solution of (B) during the crosslinking reaction, so that thereis obtained an aqueous composition in which at least a part of theoptical brightener anions are the counter-ions to at least a part of thecations of (P_(A1)) or (P_(A2)) and (B) is also entrained by (orentangled with) (P_(A1)) or (P_(A2)). The pH is chosen suitably in sucha way that salt-formation of (P_(A)) with (B) is favoured, expedientlyin the weakly acidic to distinctly alkaline range, preferably at a pH inthe range of 5 to 10, more preferably 5.5 to 9. The ratio of (B) to(P_(A)) or to its precursor (P_(PA)) is chosen in such a way that theobtained product (P_(AB)) is of anionic character, which means that theoverall anionic charge or pK due to the anionic groups present in (B)(i.e. sulpho and carboxy groups) prevails over the overall cationiccharge or pK due to the quaternary ammonium groups of (P_(A)).Preferably the number of cations, in particular of quaternary cations,in (P_(A)) or respectively in (P_(AB)) is equal or inferior to thenumber of anions introduced with (B). The ratio of total anionic groupsintroduced with (B) to the total quaternary ammonium groups in (P_(A))or respectively (P_(AB)) is e.g. in the range of 80/100 to 1000/100,preferably 100/100 to 600/100, more preferably >100/100, in particularin the range of 102/100 to 250/100, preferably 105/100 to 180/100. Theweight ratio of (B) to (P_(A)) is chosen accordingly in a suitable way;the weight ratio of (B) to a suitable precursor of (P_(A)) is chosenaccordingly. The anionicity of (P_(AB)), i.e. the overall anionicstrength of the total sulpho and carboxy groups present, prevails overthe total cationic strength of the quaternary ammonium groups present.The number of anionic groups of (B) not engaged with (P_(A)), expressedin milliequivalents per gram of (P_(AB)), is preferably equal to orsuperior, preferably by at least 0.1 meq/g, to the one of the cationicgroups of (P_(A)) not engaged with (B). The difference is e.g. in therange of 0 to 1.2 meq/g, preferably 0 to 1 meq/g, more preferably 0 to0.85 meq/g. The anionicity may be assessed e.g. by means of a “ChargeAnalyser” fitted with a photoelectric cell, by titration of a 0.1weight-% (P_(AB))-solution with a polyvinyl potassium sulphate solution(e.g. 0.00052N), using Toluidine Blue as an indicator (fromblue=cationic to pink=anionic), at pH 4, 7 and 9 (adjusted by means ofhydrochloric acid or potassium hydroxide solution).

The rate of addition and the concentration of the components isexpediently chosen in such a way that a distinct increment of theviscosity of the obtained solution takes place and the solution ofcombined product (P_(AB)) is still easily stirrable, e.g. of a viscositybelow 5000 cP, preferably in the range of 200 to 4000 cP, morepreferably 400 to 2000 cP. A suitable concentration for the solution of(B) is in the range of 5 to 70, preferably 10 to 50% by weight. Asuitable concentration for the solution of (P_(A)) is in the range of 10to 80, preferably 20 to 70% by weight. A suitable concentration for theproduced solution or dispersion of (P_(AB)) is in the range of 10 to 90,preferably 20 to 80% by weight. A particularly preferred viscosity forthese concentrations is in the range of 500 to 2000 cP. The obtainedaqueous composition (W) of (P_(AB)) is an aqueous solution, i.e. a trueor at least colloidal solution, or a dispersion. The (P_(AB))-content in(W) may vary broadly, depending in particular on the intended use andtransport form. In concentrated compositions (W) the (P_(AB))-content ise.g. in the range of 5 to 70%, preferably 8 to 50%, more preferably 10to 40% by weight. It may be used directly as produced, or—if desired—itmay be modified in salt content and/or concentration (a solution e.g. bymembrane filtration) and/or it may be combined with any further desiredcomponents, especially at least one formulation additive (F). Suitableformulation additives are in general those conventional per se, inparticular

-   -   (F₁) an antimicrobic additive,    -   (F₂) an acid, base or/and buffer salt for pH-adjustment,    -   (F₃) a hydrotrope        and/or (F₄) a defoamer.

Additives (F₁) are in particular additives for combating the damagingeffect of microorganisms, e.g. an agent that stops the growth ofdisturbing micro-organisms or a microbicide (preferably a fungicide),e.g. in a concentration of 0.001 to 0.1% by weight referred to theliquid composition.

As (F₂) are suitable any acids, bases or buffers conventional inbrightener or paper industry (e.g. alkali metal hydroxides, mineralacids or organic aliphatic acids and phosphate buffers, e.g. lithium,sodium or potassium hydroxide, sulphuric, phosphoric, acetic, citric oroxalic acid, and/or mono- or disodium phosphate) as are suitable foradjusting the pH to the desired value, which for (W), especiallyconcentrated (W), is e.g. in the range of 4 to 7, preferably 4.5 to 6.5,more preferably 5 to 6.

A hydrotrope (F₃) may be employed if desired, e.g. urea or anoligoethylene glycol, e.g. in a concentration of 1 to 20% by weight of(P_(AB)). Preferably no (F₃) is employed in (W).

Suitable defoamers as (F₄) are also conventional ones, e.g. paraffine orsilicone-based defoamers. They may be employed in very lowconcentrations, e.g. in the range of 0.001 to 0.1% by weight referred tothe liquid composition.

The viscosity of (W) is advantageously below 5000 cP, for theconcentrated compositions (W) it is preferably in the range of 200 to4000 cP, more preferably 400 to 2000 cP.

The so produced compositions (W) combine the properties of component (B)as an optical brightener and of component (P_(A)) as an internal orexternal functional additive in papermaking, for instance as aflocculant, drainage assistant, retention adjuvant or/and fixative, andare compatible with components of sizing or coating compositions, inparticular with binders, white pigments and fillers. The opticalbrightener (P_(AB)) compositions (W) of the invention provide inparticular the possibility of adding the anionic optical brightener atany time before, during or after formation of the paper web or sheet.This means e.g. that the multi-functional composition of the inventionmay be added also in the aqueous stock, without it being necessary toimmediately make the paper sheet, or it may be employed together with orin sizing compositions—also sizing compositions containing an inorganicfiller—, as per se conventionally employed for producing paper sized inthe stock or, after sheet or web formation, by application of a sizingcomposition in the size press, or it may be combined in a coatingcomposition, in particular containing an inorganic white pigment. Theterm “paper” as used herein comprises any product obtainable inpapermaking industry including not only paper as such but also heavierpaper qualities, in particular board (paper board, card board, boxboard), and cast paper shapes.

Due to the possibility of varying the ratio of (B) to (P_(A)) in a verybroad range, the optical brightener (P_(AB)) compositions orrespectively (W) of the invention offer the possibility of increasingthe proportion of (B) to (P_(A)) to very high ratios, as may be desiredfor achieving correspondingly high degrees of whiteness and also highwhiteness maxima.

According to a particular feature of the invention it is also possibleto mix products (P_(AB)) of different anionicities, in order to match acertain desired anionicity target, by mixing e.g. a higher anionicoptical brightener (P_(AB1)) with a lower anionic optical brightener(P_(AB2)) in the required ratio. For this purpose (P_(AB1)) may e.g. bean optical brightener (P_(AB)) in which the ratio of total anionicgroups of its (B) to the total quaternary ammonium groups of its (P_(A))is >150/100, in particular in the range of 180/100 to 600/100,preferably 200/100 to 400/100, and (P_(AB2)) may e.g. be an opticalbrightener (P_(AB)) in which the ratio of total anionic groups of its(B) to the total quaternary ammonium groups of its (P_(A)) is ≦150/100,in particular in the range of 80/100 to 150/100, preferably 100/100 to120/100, e.g. 100/100 to 105/100, the polymer (P_(A)) in (P_(AB1)) andin (P_(AB2)) being the same and the optical brightener (B) in (P_(AB1))and in (P_(AB2)) being the same. Where it is desired to use a somewhathigher or lower anionicity than corresponding to a certain (P_(AB)) inthe preferred anionicity, e.g. to an optical brightener (P_(AB3)) whichis an optical brightener (P_(AB)) in which the ratio of total anionicgroups of its (B) to the total quaternary ammonium groups of its (P_(A))is in the range of 105/100 to 180/100, this may be mixed with acorresponding adjusting amount of (P_(AB1)) or (P_(AB2)) respectively,the polymer (P_(A)) in (P_(AB3)) and in admixed (P_(AB1)) or (P_(AB2))being the same and the optical brightener (B) in (P_(AB3)) and inadmixed (P_(AB1)) or (P_(AB2)) being the same. For this purpose thepairs of products (P_(AB1)) and (P_(AB2)) or of products (P_(AB3)) andeither (P_(AB1)) or (P_(AB2)) are preferably employed in the form ofaqueous compsitions (W), i.e. (W₁) and (W₂) or (W₃) and (W₁) or (W₂) ofthe same concentration referred to (B).

According to one aspect of the invention the optical brightener (P_(AB))compositions (W) are suitable for the production of optically brightenedpaper by adding them in the stock before formation of the paper web orsheet or shape.

The (P_(AB))-compositions of the invention, expediently in the form ofaqueous composition as produced by the method described above, arereadily dilutable with water in any proportion. They servesimultaneously as assistants in the production of paper, in particularas fixatives, for reducing the amount of backwater components, e.g.turbidity, in backwaters (white waters) from paper production, and asoptical brighteners for producing optically brightened paper. The(P_(AB)) composition of the invention are, however, also compatible withother cationic additives or components that might be present or added inthe stock, e.g. retention aids and/or cationic surfactants, and alsoother anionic additives.

A particular feature of the invention is thus represented also by theprocess for the production of optically brightened paper wherein anaqueous (P_(AB))-solution or dispersion (W) as defined above is employedas a functional internal or external additive, optionally in thepresence of other cationic additives.

The invention thus provides also a method for producing paper, inparticular a paper web or sheet, from aqueous stock, wherein (P_(AB)) orrespectively (W) is employed as a multifunctional adjuvant, especiallyas an optical brightening agent and as a fixative. As an aqueous stockthere is intended any stock, in particular cellulosic stock, as employedfor papermaking and wherein the pulp suspension may derive from anyorigin as conventionally employed for papermaking, e.g. virgin fiber(chemical or mechanical pulp), machine broke (in particular coatedbroke) and reclaimed paper (especially deinked and optionally bleachedreclaimed paper). The aqueous paper pulp or stock may also containfurther additions as may be desired for a certain quality, such assizing agents, fillers, flocculating agents, drainage and/or retentionassistants, which are preferably added in any desired sequence before,simultaneously with or after the addition of (P_(AB)). The stockconcentration may vary in any conventional range as suitable for theemployed pulp, machine, process and desired paper quality, e.g. in therange of 0.4 to 10%, preferably 0.8 to 6%, by weight of dry pulp.According to a particular feature of the invention there is employed apulp from coated broke and/or bleached, deinked reclaimed paperoptionally blended with other pulp.

The optical brighteners (P_(AB)) are preferably employed in aconcentration in the range of 0.05 to 0.5% by weight, more preferably0.1 to 0.4% by weight referred to dry pulp. The pH may be in the weaklybasic to distinctly acidic range, preferably in the range of pH 4 to pH8, more preferably pH 5 to pH 7. The paper may be produced using anyconventional papermaking machines and in a manner conventional per se.The resulting backwater is of reduced contaminants content, inparticular of reduced turbidity, and consequently the respective BODand/or COD values are also reduced.

According to a further aspect of the invention the compositions (P_(AB))are suitable for the production of optically brightened sized or/andcoated paper by adding them in sizing or/and coating compositions whichare applied to the paper substrate after formation of the paper web orsheet or other shape.

The sizing compositions may contain conventional components, inparticular binders and optionally co-binders, fillers, pigments,dispersants and/or further adjuvants conventional per se.

Any binders and co-binders, conventional in sizing compositions may beemployed, e.g. optionally modified natural products, e.g. starches (e.g.starches or starch derivatives, in particular neutral starches, cationicstarches or anionic starches), casein, soy bean protein or modifiedcellulose (carboxymethylcellulose, methylcellulose,hydroxyethylcellulose), or synthetic latices, e.g. styrene/butadienepolymers, acrylic polymers, vinylacetate polymers, polyvinylalcohol,polyvinylpyrrolidone and optionally polyurethanes. They may be employedin concentrations conventional pr se in sizing compositions, preferablyin the range of 1 to 20%, more preferably 2 to 12% by weight of theaqueous sizing composition.

If desired the sizing compositions may contain inorganic fillers orpigments. As fillers or pigments there may be employed conventionalones. Preferably, however, they do not contain any fillers and, morepreferably, also no pigments.

The optical brighteners (P_(AB)) are preferably employed in aconcentration in the range of 0.02 to 0.5% by weight, more preferably0.05 to 0.2% by weight referred to dry paper. The pH may be in theweakly basic to distinctly acidic range, preferably in the range of pH 4to pH 8, more preferably pH 5 to pH 7. The paper web or sheet or othershape may be produced using any conventional papermaking machines.

The coating compositions may contain conventional components, inparticular inorganic pigments, binders (e.g. selected from thosementioned above), dispersants (e.g. polyacrylates or polyphosphates) andoptionally further adjuvants conventional per se.

The inorganic pigments comprise in general known inorganic substances asusually employed as white pigments or fillers (or loading agents), andwhich more particularly are conventionally employed in non-coloured formin papermaking.

The inorganic pigments or fillers may be any such substances, naturallyoccurring and optionally physically modified, or synthetically produced,and preferably as employed in particular in paper coatings or as fillersor loading agents in the paper sheet, as added e.g. in the size or alsoin the paper pulp suspension. They may include mineral substances andsynthetically produced inorganic substances, such as silica, alumina,titanium dioxide, zinc oxide and sulphide, and inorganic salts, e.g.silicates, aluminates, titanates, sulphates and carbonates, of lowvalence metal ions, mainly of alkali metal ions, alkaline earth metalions or earth metal ions, especially of sodium, potassium, magnesium,calcium, barium and/or aluminium. The following may be mentioned asexamples: titanium dioxides (rutile, anatase), potassium titanates, zincoxide, zinc sulphide, lithopone, calcium sulphates (gypsum oranhydrite), various forms of silica (e.g. amorphous silica such asdiatomite), alumina trihydrate, sodium silico-aluminate, talc(MgO.4SiO₂.H₂O), barium sulphate (baryte, blanc fixe), calciumsulphoaluminate (satin white), chrysotile, china clay in various degreesof whiteness (mainly comprising Al₂O₃.SiO₂.H₂O and optionally furthermetal oxides such as iron oxide, titanium dioxide, magnesium oxide,calcium oxide, sodium oxide and/or potassium oxide) and calciumcarbonate in various forms (mineral natural form or syntheticprecipitated and/or crystallised forms). They may be employed in theforms as commercially available, in particular of various degrees ofwhiteness, e.g. of a whiteness >80, mostly >82 (measured according toISO methods), but also less white products may be used, e.g. of awhiteness ≦82, or even ≦80, e.g. in the range of 70 to 80 (e.g.CIE-whiteness, as may be measured spectrophotometrically).

The particle size of the pigment or filler may range in usual scopes,e.g. in the range of 0.1 to 40 μm, as obtainable by conventionalmethods, e.g. by grinding and/or milling and/or—if required—sieving andscreening, or by suitable precipitation and/or (micro)crystallisationmethods. Commercially available products mostly contain in general acertain proportion of particles smaller than 0.1 μm (dust) and/or somegranules larger than 40 μm; preferably these larger size components are≦20% by weight, more preferably ≦10% by weight. Preferably the averageparticle size of such inorganic pigments is within the range of 0.1 to20 μm, more preferably 0.2 to 10 μm, most preferably 0.2 to 5 μm,preferably at least 75%, more preferably ≧80% of the particles beingwithin these ranges. Preferred inorganic pigments and fillers have e.g.a specific surface area in the range of 5 to 24 m²/g, preferably 7 to 18m²/g. Among the mentioned pigments and fillers are preferred thosecomprising carbonates, in particular calcium carbonates.

The inorganic pigments and fillers may be employed in commerciallyavailable forms, which may also comprise a conventional dispersant orwetting agent, on its surface, e.g. polyphosphates, in a suitable lowconcentration as usual e.g. <0.5% by weight, preferably <0.3% by weight.For the purpose of the invention the presence of such a surfactant isnot essential and the pigment may also be exempt of a dispersant orwetting agent. As mentioned above, the pigment may be employed in theforms as commercially available, in particular it may be employed in dryform or in the form of a concentrated aqueous slurry, e.g. with a solidscontent in the range of 40 to 70% by weight.

For the production of a coating composition the optical brightener(P_(AB)) composition (W) may be mixed with conventional coatingcomposition components exempt of optical brighteners, in particularpigments, dispersants, adhesives and water and optionally furtheradjuvants such as anti-foam agents or defoamers, flow modifiers,lubricants and optionally surface finishing agents or adjuvants.

If desired, a white pigment or filler pretreated with (P_(AB)) may beproduced in the form of an aqueous slurry or even in dry form. For thispurpose the inorganic white pigment or filler may e.g. be mixed with(P_(AB)) or respectively (W) in aqueous medium or a solution ordispersion (W) of (P_(AB)) may be sprayed on a dry inorganic whitepigment or filler powder with mixing. The produced aqueous suspensionmay, if desired, be filtered and dried to a (P_(AB))-containing whitepigment or filler in dry, particulate form of corresponding particlesize. If desired it may be agglomerated to larger agglomerate particles,e.g. by compaction e.g. to granules, pellets or tablets. This process ispreferably carried out substantially in the absence of furtherfunctional additives that would interfere in a disturbing way with thereaction, in particular in the absence of other functional papermakingadditives and components (such as resins, fibres and/or paper-sizecomponents). The weight ratio of (P_(AB)) to inorganic pigment orfiller—referred to the respective dry forms—may range broadly, dependingon the desired use and effect; it may e.g. range in the scope of0.01:100 to 10:100, preferably 0.2:100 to 5:100, more preferably 0.3:100to 4:100. For compacted dry forms this weight ratio is preferably in therange of 0.01:100 to 3:100, more preferably 0.2:100 to 2:100.

The optical brightener composition (P_(AB)) may be applied in the formof an aqueous solution or dispersion (W) e.g. of a concentration in therange 0.1 to 700 g/l, to the inorganic pigment by any suitable method.If the inorganic pigment is used in the form of an aqueous slurry, the(P_(AB))-composition (W) is preferably a concentrated solution ordispersion—e.g. of a concentration in the range 20 g/l to 700 g/l,preferably in the range of 50 g/l to 600 g/l—and may be mixed with it inthe desired proportion e.g. by plain stirring and optionally withheating or cooling, e.g. at a temperature in the range of 5 to 60° C.,preferably 10 to 40° C., more preferably with slight heating e.g. in thetemperature range of 25 to 40° C. or at ambient conditions without anyheating or cooling. If the inorganic pigment is in the dry form, asprayable, preferably more diluted aqueous solution or dispersion of(P_(AB))—e.g. of a concentration in the range of 0.1 to 40 g/l,preferably 0.5 to 20 g/l—may e.g. be applied by spraying and mixing,optionally with heating or cooling, e.g. at a temperature in the rangeof 5 to 60° C., preferably 10 to 40° C., more preferably with slightheating e.g. in the temperature range of 25 to 40° C., or at ambientconditions without any heating or cooling. The pH of the aqueouscomposition (W) of (P_(AB)) may range broadly, e.g. from the weaklyacidic to weakly basic range, in particular from pH 5 to pH 8,preferably pH 5.5 to pH 7.5.

The so modified white pigments or fillers, which are the products of theapplication of (P_(AB)) or respectively (W) to the inorganic whitepigment or filler, combine the physical properties of the inorganicwhite pigment or filler with the chemical properties of (P_(AB)); i.e.they may be used as pigments or fillers in various stages of paperproduction and, due to the possibility of increasing the proportion of(B) to (P_(A)) in (P_(AB)) to a high degree, they provide thepossibility of achieving very high degrees of whiteness and also veryhigh whiteness maxima, further they favour drainage, retention andfixation, and the compacted forms are readily dispersible in water togive a regular suspension that may be used for producing brightener andfiller or white-pigment-containing coating masses, size liquors or paperpulp suspensions. These brightener-treated white pigments are alsoreadily compatible with other cationic products that might be used inpaper production, such as drainage aids, retention assistants andfixatives, e.g. with cationic starches.

The invention thus provides also a method for producing paper, inparticular a paper web or sheet, from aqueous stock, wherein a(P_(AB))-treated white pigment or filler is employed as a white pigmentor filler.

By the use of (P_(AB)) or respectively (W) there may also be achieved animprovement of the efficiency of other wet-end additives, especiallycationic ones, such as flocculants, retention assistants or drainageassistants, and there may be obtained paper of optimum quality while theoccurrence of paper breakings due to disturbing anionic contaminants iscorrespondingly reduced, and the efficiency of the optical brightener(B) is optimal and there is obtainable paper of very regular whitenessin high yield. The so produced paper is suitable as graphic paper andmay in particular be employed as a substrate for ink-jet-printing.

In the following Examples parts and percentages are by weight, if nototherwise indicated; parts by weight relate to parts by volume as gramsto milliliters; the temperatures are indicated in degrees Celsius; inApplication Examples D and E ° SR signifies degrees Schopper-Riegler andthe p % and size percentages relate to the weight of the startingaqueous pulp suspension.

EXAMPLE 1

In a closed vessel which is fitted with an overhead stirrer, acondenser, a dropping funnel and a calibrated thermometer, 70.2 parts ofsorbitol are mixed with 35.5 parts of glycerol and heated to 90° C. toform a solution. The solution is cooled to 80° C. and 0.5 part of borontrifluoride acetic acid complex (M_(W) 187.91) is added and stirring iscontinued until the catalyst is fully dispersed throughout the reactionmixture. 10 parts of epichlorohydrin are added at 80° C., so that anexotherm results. Further 202.1 parts of epichlorohydrin are then addedover 1 hour at 80–85° C., with cooling. The reaction mixture is thencooled to 30° C., the air in the vessel is evacuated, 86.8 parts of anaqueous 60% dimethylamine solution are drawn in and the reaction mixtureis heated slowly to 90° C. and held for one hour at 80–90° C. The vacuumis then released and the reaction mixture is cooled to 60° C. At thistemperature 971.0 parts of an aqueous 18% solution of the sodium salt ofthe optical brightener of formula

(produced using L-aspartic acid) and 90.4 parts of sodium hydroxide, inthe form of a 30% aqueous solution, are added at 65–70° C. The mixtureis held at 65–70° C. and it slowly thickens as it polymerises. When thereaction mixture reaches the viscosity of 1000 cP the reaction isstopped by the addition of 20 parts of formic acid to give a pH of 5.5.

EXAMPLE 2

The procedure described in Example 1 is repeated, with the differencethat instead of 971.0 parts of the optical brightener solution there areemployed 1294.8 parts thereof.

EXAMPLE 3

The procedure described in Example 1 is repeated, with the differencethat instead of 971.0 parts of the optical brightener solution there areemployed 1553.6 parts thereof.

EXAMPLE 4

The procedure described in Example 1 is repeated, with the differencethat instead of 971.0 parts of the optical brightener solution there areemployed 1942.0 parts thereof.

EXAMPLES 5–8

The procedures described in each of Examples 1–4 is repeated, with thedifference that instead of the optical brightener of formula (1)produced with L-aspartic acid there is employed the optical brightenerof formula (1) produced with racemic aspartic acid.

EXAMPLE 9

The procedure described in Example 1 is repeated, with the differencethat instead of the 971.0 parts of the 18% solution of the sodium saltof the optical brightener of formula (1) there are employed 989.0 partsof an 18% solution of the sodium salt of the optical brightener offormula

(produced using L-glutamic acid).

EXAMPLES 10–12

The procedure described in Examples 2–4 is repeated, with the differencethat instead of the indicated quantity of the 18% solution of theoptical brightener of formula (1) there is employed the equivalentamount of the 18% solution of the optical brightener of formula (2).

APPLICATION EXAMPLE A

Sizing solutions are prepared by adding a predetermined amount of theproduct of Example 1 (0, 1.25, 2.5, 5, 7.5 and 10 mmol/kg referred tothe optical brightener) to a stirred aqueous solution of a typicalsize-press starch (typically a cationic starch, such as CATO-SIZE 470from National Starch, or an anionic starch, such as Perfectamyl fromTunnel Avebe) at 60° C. The solution is diluted with water to a starchcontent concentration of 10%. The sizing solution is poured between themoving rollers of a laboratory size-press and applied to a commercial 75g/m² neutral-sized (with conventional alkyl ketene dimer), bleachedpaper base sheet, to an uptake of 30% by weight referred to the dryweight of the substrate. The treated paper is dried for 5 minutes at 70°C. in a flat bed drier. The dried paper is allowed to condition, thenmeasured for CIE whiteness on a calibrated Datacolor ELREPHO 2000spectrophotometer. The measured values show a surprisingly highwhiteness degree and yield for the sheets treated with the product ofExample 1.

APPLICATION EXAMPLE B

A coating composition is prepared containing 3000 parts chalk (fine,white, high purity calcium carbonate with a density by ISO 787/10 of2.7, commercially available under the trade name HYDROCARB OG ofPlüss-Stauffer AG, Oftringen, Switzerland), 1932 parts water, 18 partsanionic dispersing agent (sodium polyacrylate), and 600 parts latex (acopolymer of n-butyl acrylate and styrene latex of pH 7.5–8.5,commercially available under the trade name ACRONAL S320D). Apredetermined amount of the product of Example 1 (0, 0.313, 0.625,0.938, 1.25 and 1.875 mmol/kg referred to the optical brightener) isadded with stirring to the coating composition, and the solids contentis adjusted to 55% by the addition of water. The so prepared coatingcomposition is then applied to a commercial 75 g/m² neutral-sized (withconventional alkyl ketene dimer), bleached paper base sheet, using anautomatic wire-wound bar applicator with a standard speed setting and astandard load on the bar. The coated paper is dried for 5 minutes at 70°C. in a hot air flow. The dried paper is allowed to condition, thenmeasured for CIE whiteness on a calibrated Datacolor ELREPHO 2000spectrophotometer. The measured values show a surprisingly highwhiteness degree and yield for the sheets treated with the product ofExample 1.

APPLICATION EXAMPLE C

The procedure described in Application Example B is repeated, with thedifference that instead of 3000 parts of the chalk HYDROCARB OG thereare employed 3000 parts of the chalk HYDROCARB 90 (from Omya UK), andthat 150 parts of anionic starch (Perfectamyl A4692, from Tunnel Avebe)are further added.

APPLICATION EXAMPLE D

200 g of a pulp suspension (2.5% aqueous suspension of a 50% mixture ofbleached soft wood and hard wood pulps beaten to a freeness of about 20°SR) is measured into a beaker and stirred. The suspension is stirred forone minute and p % of the product of Example 1 is added (p=0, 0.1, 0.2,0.4, 0.8, 1, 1.4, 1.8 and 2; p=0 representing the blank). After theaddition the mixture is stirred for a further 0.5 minutes and then 1.7%(3.4 g) of neutral size is added (typically a dispersion of 2.5 g ofAquapel 360×in water—Aquapel 360X is an alkylketene dimer sizesuspension from Hercules Ltd.). After the addition of the size aretention aid may be added—typically Cartaretin PC. The mixture is thendiluted to one litre and the paper sheet is formed on a laboratory sheetformer (basically this is a cylinder with a wire gauze at the bottom—thecylinder is partly filled with water, the pulp suspension is added, airis then blown through to ensure the pulp is well dispersed, a vacuum isthen applied and the pulp slurry is pulled through the wire to leave apaper sheet, this sheet is removed from the wire and pressed and dried).The whiteness of the sheet is measured using a Datacolor ELREPHO 2000spectrophotometer. The measured values show a surprisingly highwhiteness degree and yield for the sheets treated with the product ofExample 1.

APPLICATION EXAMPLE E

200 g of a pulp suspension (2.5% aqueous suspension of a 50% mixture ofbleached soft wood and hard wood pulps beaten to a freeness of about 20°SR) is measured into a beaker and stirred. The suspension is stirred forone minute and p % of the product of Example 1 is added (p=0, 0.1, 0.2,0.4, 0.8, 1, 1.4, 1.8 and 2; p=0 representing the blank). After theaddition the mixture is stirred for a further 5 minutes and then 2% ofrosin size solution is added (typically “T size 22/30” from Hercules),the mixture is stirred for a further 2 minutes and then 3 ml of alumsolution (50 g alum in 1 litre water) are added and the mixture isstirred for a further 2 minutes. The mixture is then diluted to onelitre and the paper sheet is formed on a laboratory sheet former. Thewhiteness of the sheet is measured using a Datacolor ELREPHO 2000Spectrophotometer. The measured values show a surprisingly highwhiteness degree and yield for the sheets treated with the product ofExample 1.

Analogously as the product of Example 1, the products of each ofExamples 2 to 12 are employed in the above Application Examples A, B, C,D and E.

1. An optical brightener (P_(AB)) of formula (I)

wherein each n independently is 1 or 2, the group SO₃M shown with thefloating bond is linked to the position 4 or 5, each M independently isan equivalent of a non-chromophoric cation and each M′ independently ishydrogen or M, at least a part of the cations M of (P_(AB)) are cationicgroups of a polycationic polyol/epichlorohydrin/amine polymer (P_(A)),containing quaternary ammonium groups in salt form as heteroatomic ringmembers or chain members, the remaining cations M of (P_(AB)) areselected from the group consisting of alkali metal cations,unsubstituted ammonium and ammonium substituted with C₁₋₃-alkyl or/andC₂₋₃-hydroxyalkyl, the polycationic polymer (P_(A)) is a polymer whichis at least in part crosslinked over one or more of its quaternaryammonium groups, the remaining counterions to the cationic groups of(P_(A)) being non-chromophoric anions of low molecular acids, and theratio of the total anionic groups in the anionic optical brightenerportion of (P_(AB)) to the total of cationic ammonium groups in thepolycationic polymer (P_(A)) portion of (P_(AB)) is ≧80/100.
 2. A liquidaqueous optical brightener composition (W) comprising an opticalbrightener (P_(AB)) according to claim
 1. 3. A liquid aqueouscomposition (W) according to claim 2, further comprising at least oneformulation additive (F) selected from the group consisting of (F₁) anantimicrobic additive, (F₂) an acid, base and/or buffer salt forpH-adjustment, and (F₄) a defoamer.
 4. An optical brightener (P_(AB))according to claim 1, wherein the ratio of the total anionic groups inthe anionic optical brightener portion of (P_(AB)) to the total ofcationic ammonium groups in the polycationic polymer (P_(A)) portion of(P_(AB)) is in the range of 100/100 to 600/100.
 5. Process for theproduction of a liquid aqueous optical brightener composition (W)according to claim 2, comprising the step of adding an aqueous solutionof (B) an anionic optical brightener of the formula (II)

wherein each n independently signifies 1 or 2, and the group SO₃H shownwith the floating bond is linked to the position 4 or 5, in free acid oralkali metal or/and ammonium salt form, wherein ammonium isunsubstituted or substituted with C₁₋₃-alkyl or/and C₂₋₃-hydroxyalkyl,to an aqueous solution of (P_(A)) a polycationicpolyol/epichlorohydrin/amine polymer containing quaternary ammoniumgroups in salt form as heteroatomic chain members or ring members of thepolymer, which is at least in part crosslinked over one or more of thesequaternary ammonium groups and in which the counter-ions to the cationicquaternary ammonium groups are anions selected from the group consistingof mineral acids, anions of low molecular carboxylic acids and anionsderiving from a quaternizing agent, in such an equivalents ratio thatthe total anionic groups in the anionic optical brightener (B) to thetotal of cationic ammonium groups in the polycationic polymer (P_(A)) is≧80/100, and the obtained product (P_(AB)) is in the form of a liquidaqueous composition (W).
 6. Process according to claim 5, furthercomprising the step of adding one or more formulation additives (F)selected from the group consisting of (F₁) an antimicrobic additive,(F₂) an acid, base and/or buffer salt for pH-adjustment, and (F₄) adefoamer after completion of the production of (P_(AB)).
 7. A method foroptically brightening a substrate comprising the step of applying to orincorporating in the substrate an optical brightener according toclaim
 1. 8. The method according to claim 7, wherein the substrate ispaper or board.
 9. A brightener-containing composition comprising awhite pigment and an optical brightener (P_(AB)) according to claim 1,wherein the composition is in the form of an aqueous slurry or in dryform.
 10. A method for optically brightening paper comprising the stepof applying to the paper a brightener-containing composition, whereinthe brightener-containing composition comprises white pigment or afiller, and an optical brightener (P_(AB)) according to claim 1, whereinthe brightener-containing composition is in the form of an aqueousslurry or dry form.
 11. Paper produced by the process according to claim8.
 12. A substrate for ink-jet printing comprising paper according toclaim
 11. 13. Process for the production of a liquid aqueous opticalbrightener composition (W) according to claim 2, comprising the step ofadding an aqueous solution of (B), an anionic optical brightener of theformula (II)

wherein each n is signifies 1 or 2, and the group SO₃H shown with thefloating bond is linked to the position 4 or 5, in the form of the freeacid or alkali metal salt, to a precursor (P_(PA)) of (P_(A)): (P_(A)) apolycationic polyol/epichlorohydrin/amine polymer containing quaternaryammonium groups in salt form as heteroatomic chain members or ringmembers of the polymer, which is at least in part crosslinked over oneor more of these quaternary ammonium groups and in which thecounter-ions to the cationic quaternary ammonium groups are anionsselected from the group consisting of mineral acids, anions of lowmolecular carboxylic acids and anions deriving from a quaternizingagent, before completion of polymerisation and/or crosslinking, and thepolymerisation and/or crosslinking reaction is completed in the presenceof (B), to give a solution or dispersion of the product (P_(AB)) whichis a polymer (P_(AB)′) containing (B) at least in part in entrained orentangled salt form, in such an equivalents ratio that the total anionicgroups in the anionic optical brightener (B) to the total of cationicammonium groups in the polycationic polymer (P_(A)) is ≧80/100, and theproduct (P_(AB)) is in the form of a liquid aqueous composition (W). 14.A brightener-containing composition comprising a filler and an opticalbrightener (P_(AB)) according to claim 1, wherein the composition is inthe form of an aqueous slurry or in dry form.